The invention relates to a central or eccentric ring seal arrangement, and in particular to a seal arrangement for a rotary slide valve or the like with convex surface.
Shut-off elements according to the invention are cocks or rotary slide valves which have a shutting-off part referred to as a cock plug or cone plug, which may be of conical, cylindrical or spherical design. Depending on the type, the cock plug has passages in the shape of an I, L, T, X or V, which are brought into the desired operating position by turning of the plug. The sealing-off of such rotary slide valves from the outside and the connecting lines among them often present problems. Such a shut-off element, referred to as a pipe switch, has become known from German Offenlegungsschrift No. 2,148,557, in which the end openings of the cone plug are provided with inflatable seals embracing the latter, which in the inflated state are firmly held in place between plug and inside wall of the housing. On pressure relief, the ring seal withdraws into the annular groove and no longer brushes against the inside wall of the housing when the plug is swivelled. As a result, an easy swivelling of the cone plug, associated with little expenditure of force, is possible. The pressurization of the ring seal takes place by means of valves which can be controlled independent on the swivel position of the plug. The advantage of this arrangement is that only the two end openings of the cone plug are provided with ring seals. The number of traction openings and a corresponding sealing-off in this region is consequently immaterial.
What is disadvantageous about this known arrangement are the annular grooves, to be produced only on special machines, in the case of such a cone plug. In addition, only a type of inflatable tube comes into consideration as seal, which tube can generally not assume any sealing function itself. Therefore, an additional sleeve is provided as sealing element between the inflatable seal and the inside of the housing. This sleeve, however, constantly rubs in some form against the inside wall of the housing, which can lead to a stiffness and to wear. Also disadvantageous is a complex swing joint for the air supply to the cone plug.
In the case of a further known design according to German Offenlegungsschrift No. 1,550,132, a shut-off cock has become known which uses a ring seal in the respective end opening of the housing connection flange for the sealing-off between housing and cone plug, the ring seal being arranged in a groove running radially with respect to the longitudinal axis of the bore and acting against an additional thrust ring, which is braced against the cone plug itself. This type of seal has the disadvantage that it leads to a stiffness of the cone plug due to its necessary prestress.
The same problems described above also arise in principle in the case of all devices with a housing opening to be sealed off which is to be closed by a slide valve or the like running transversely to the housing opening. During the opening or closing operation, part of the ring seal surrounding the housing opening is always without an opposing wall, which in certain circumstances can lead to the seal springing out from the annular groove. In addition, the seal is constantly subjected to shearing stress during closing of the opening, which can lead to lateral damage or to a tearing-out of the seal.
The problem addressed by the invention may occur in rotary slide valves and multi-way valves of any type in which openings are to be closed pressure tightly by a moved machine component. Equally, the problem may also occur in the case of longitudinal slide valves to be sealed off.